<html>
    <head>
        <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
        <script src="js/index.js"></script>        
        <link rel="stylesheet" type="text/css" href="css/index.css">
    </head>
    <button class="btn" onclick="cl();">按钮</button>
</html>
